Electro-optical stimulation/measurement

ABSTRACT

An electro-optical system includes an array including a plurality of optical fibers and a plurality of electrodes, and an insulator. The optical fibers are configured to transmit light, the optical fibers being mechanically coupled at distal ends in a distal arrangement and mechanically coupled at proximal ends in a proximal arrangement. The plurality of electrodes are substantially coaxially disposed with at least portions of corresponding optical fibers, the electrodes being electrically conductive, with the electrodes and optical fibers being disposed in pairs, thereby being pair components, with one of the pair components of each pair being disposed about a radial periphery of the other pair component. The insulator is disposed between the plurality of electrodes and configured to inhibit transfer of electrical energy between the plurality of electrodes.

STATEMENT AS TO FEDERALLY-SPONSORED RESEARCH

This invention was made at least in part with Government support underGrant No. GM48142, awarded by National Institutes of Health. TheGovernment has certain rights in this invention.

FIELD OF THE INVENTION

The invention relates to dual sensor/actuator systems and moreparticularly to combination optical and electrical sensor/actuatorarrays.

BACKGROUND OF THE INVENTION

There is a virtually endless list of applications for devices that canprovide stimuli to and/or receive output from and/or detect states ofany number of systems, including living beings, machines, chemicals,etc. For example, conductors can deliver energy to systems, such asdelivering electricity to a muscle to stimulate contraction of themuscle. Also, conductors can be used to sense electric impulses producedinternally to a body to determine when or whether the body hasinstructed the muscle to contract. Optical fibers can deliver light tosystems, e.g., to cause a reaction that can be detected by opticalfibers, or other means such as electrical conductors. Besideelectrochemical devices, optical fibers and optical fiber bundlesallowing simultaneous sensing and imaging have been used increasinglyfor a variety of different applications.

As technology advances, there is a push toward smaller, faster, morequickly responsive actuators and sensors. Microelectrodes provide smallvoltage-drop devices for transferring energy, be it for providingstimuli or measuring electrical output. Microelectrodes are gainingincreased importance in electrochemical analysis and sensor technologyas their small size leads to small faradaic currents, reduced iR dropand steady-state diffusion currents.

SUMMARY OF THE INVENTION

In general, in an aspect, the invention provides an electro-opticalsystem including an array including a plurality of optical fibers, aplurality of electrodes, and an insulator. The optical fibers areconfigured to transmit light, the optical fibers being mechanicallycoupled at distal ends in a distal arrangement and mechanically coupledat proximal ends in a proximal arrangement. The plurality of electrodesare substantially coaxially disposed with at least portions ofcorresponding optical fibers, the electrodes being electricallyconductive, with the electrodes and optical fibers being disposed inpairs, thereby being pair components, with one of the pair components ofeach pair being disposed about a radial periphery of the other paircomponent. The insulator is disposed between the plurality of electrodesand configured to inhibit transfer of electrical energy between theplurality of electrodes.

Implementations of the invention may include one or more of thefollowing features. The system further includes an electrical apparatuscoupled to at least some of the plurality of electrodes and configuredto at least one of transmit electrical energy to, and receive electricalenergy from, the at least some of the plurality of electrodes, and anoptical apparatus configured and disposed to receive light from theproximal ends of the optical fibers. The electrical device is coupled toless than all the plurality of electrodes. The electrical device iscoupled to a percentage of the electrodes such that diffusional overlapat distal ends of the electrodes will be substantially negligible. Theelectrical device is coupled to approximately 20-30% of the electrodes.The electrode of each pair is disposed about the radial periphery of thefiber of each pair. An edge-to-edge spacing between any two electrodescoupled to the electrical apparatus is greater than about 10 times atypical diameter of one the plurality of electrodes. The optical fiberof each pair is disposed about the radial periphery of the electrode ofeach pair. A center-to-center spacing between any two electrodesdisposed coaxially with the at least some of the plurality of opticalfibers is greater than about 10 times a typical diameter of one theplurality of electrodes. The distal ends of the optical fibers correlateto the proximal ends of the optical fibers in a known manner. The distalarrangement and the proximal arrangement are substantially similar. Theelectrical apparatus is configured to at least one of transferelectrical energy to, and receive electrical energy from, the at leastsome of the plurality of electrodes as a group. The electrical apparatusis configured to at least one of transfer electrical energy to, andreceive electrical energy from, the at least some of the plurality ofelectrodes individually. The electrodes comprise electrically-conductivematerial coating an outer surface of the optical fibers.

In general, in another aspect, the invention provides a method ofstimulating and sensing an object, the method including providing energyin a first form to the object through at least one of a plurality offirst energy transmitters disposed in a first array at least at distalends of the first energy transmitters, the first form of energy beingone of electrical and optical, and sensing energy in a second form,produced by the object, through at least one of a plurality of secondenergy transmitters disposed in a second array at least at distal endsof the second energy transmitters, the first and second energytransmitters being mechanically coupled together and coaxially disposedat least at their distal ends, the second form of energy being one ofelectrical and optical, the second form of energy being different thanthe first form of energy.

Implementations of the invention may include one or more of thefollowing features. The first form of energy is electrical and the firstenergy transmitters are microelectrodes, and wherein the providingenergy includes providing energy to all of the plurality of first energytransmitters. The first form of energy is electrical and the firstenergy transmitters are microelectrodes, and wherein the providingenergy includes selectively providing energy to a portion of theplurality of first energy transmitters. The method of claim 16 whereinthe providing energy includes providing energy to the portion of theplurality of first energy transmitters such that diffusional overlap ofthe energy at distal ends of the portion of the plurality of firstenergy transmitters is substantially negligible. The first form ofenergy is electrical and the first energy transmitters aremicroelectrodes, and wherein the providing energy includes providingdifferent amounts of energy to different ones of the plurality of firstenergy transmitters. Either the first or the second energy transmittersare electrodes, the method further comprising providing electricalenergy through the electrodes to kill living tissue in the object in avicinity of distal ends of the electrodes. The method further includesprocessing the second energy to determine an image of at least a portionof the object. The method further includes providing energy in thesecond form to the object through at least one of the second energytransmitters. The providing energy in the first form and the providingenergy in the second form occurs concurrently. The second energytransmitters are optical fibers, and the sensing includes sensingoptical energy transmitted by at least two of the optical fibers. Thefirst energy transmitters are optical fibers and the providing includestransmitting optical energy through less than all of the optical fibers.

In general, in another aspect, the invention provides an electro-opticalactuator/sensor system including optical means for delivering light toan optical-fiber array, electrical means for delivering electricitythrough an electrical array of microelectrodes, the electrical meanscomprising electrically-conductive cladding of the optical fibers in theoptical-fiber array, an electrical apparatus coupled to the electricalmeans and configured to transfer electrical energy between theelectrical apparatus and selected ones of the microelectrodes, and anoptical apparatus configured and disposed to transfer light between theapparatus and the optical-fiber array.

Implementations of the invention may include one or more of thefollowing features. Distal and proximal ends of the optical fibers andelectrodes are coherently related. The electrical apparatus is coupledto transfer electrical energy to about 20-30% of the electrodes. Distalends of the electrodes are disposed proximate to distal ends of theoptical fibers and are separated from each other such that diffusionaloverlap associated with the electrodes is substantially negligible.

Various percentages or portions of energy transmitters in arrays can bestimulated to reduce or eliminate effects of diffusional overlap in asubject receiving energy from the arrays. As diffusional overlap isdependent upon size of the element radiating energy, and time ofstimulation/activation, the number of elements activated may be adjustedto reduce or eliminate diffusional overlap. All elements can beactivated if the separation between elements combined with the size ofelements, amount of time of stimulation, size of species, viscosity ofsolution, applied current amount, and any other influencing factors,results in little or no diffusional overlap. Preferably, less than allelements are stimulated to help ensure negligible overlap. Anypercentage under 100% can be used if, when combined withdiffusional-overlap-influencing factors (e.g., element size, current,solution viscosity, species size, and time of stimulation), the overlapcan be neglected. Arrays with approximately 50% and between 20-30% ofthe elements activated proved successful in acceptably controllingdiffusional overlap.

The invention also provides a method of specifically stimulating atarget cell in a population of non-target cells by detecting an opticalsignal (e.g., a signal elaborated after binding of the cell to adetectably labeled antibody or other cell-specific ligand) to identifythe target cell and deliver an electrical current to the cell. Theelectrical current preferably is not delivered to a non-target cell,which may be present in the population of cells (e.g., adjacent to thetarget cell). The electrical current stimulates the target cell totransduce an intracellular or extracellular signal, e.g, the target cellis stimulated to produce a neurotransmitter or cytokine. The target cellmay also be stimulated to proliferate. Alternatively, the target cell isidentified electrically and stimulated by focusing an optical beam onthe target cell.

A method of specifically destroying or inhibiting the growth of a targetcell in population of non-target cells is carried out by detecting anoptical signal (as described above) to identify the target cell anddelivering an electrical current to the cell thereby inhibitingproliferation of the target cell or destroying the target cell. Forexample, the target cell is a cancer cell and non-target cells arehealthy (non-tumor) cells present in a bodily tissue. The electricalcurrent is preferably not delivered to a non-target cell, i.e., thetarget cell is destroyed while sparing non-target (e.g, healthy) cells,which are present in the heterogeneous cell population or bodily tissue.The specificity of the cell targeting method reduces undesirable sideeffects (e.g., death of healthy cells) often associated with knowncancer therapies.

Various aspects of the invention may provide one or more of thefollowing advantages. Higher currents than using a single ring-shapedmicroelectrode may be achieved without losing benefits gained byminiaturization. Rapid response time, steady state diffusion layer, andsmall iR drops may be achieved for electric transmission while providinghigh currents. Uses and advantages of microelectrodes can be combinedwith imaging properties of optical fiber bundles. Diffusional overlap ofmicroelectrodes may be reduced/limited. Optical and electronic,including electrochemical, stimulation and measuring may be performedwith a single apparatus. Microelectrode sensor/actuator signal-to-noiseratio may be improved.

These and other advantages of the invention, along with the inventionitself, will be more fully understood after a review of the followingfigures, detailed description, and claims.

BRIEF DESCRIPTION OF THE FIGURES

FIG. 1 is a simplified diagram of an electro-optical system forproviding electrical and/or optical stimuli and measuring electricaland/or optical output.

FIG. 2 is a schematic diagram of an electro-optical array shown in FIG.1.

FIG. 3 is a block flow diagram of a process of assembling the arrayshown in FIG. 2.

FIG. 4 is a block flow diagram of a process of using the system of FIG.1.

FIG. 5 is an FE-SEM image of an optical fiber embedded in epoxy of thearray shown in FIG. 1.

FIG. 6 is an FE-SEM image of an outer gold layer of a fiber/electrodepair shown in FIG. 2.

FIGS. 7-9 are cyclic voltammograms of a disk electrode (a) with a 25 mdiameter, and of a fiber/gold ring electrode (b) (FIG. 7), a microarraywith a self-assembled thiol monolayer (FIG. 8), and a microarray withouta self-assembled thiol monolayer (FIG. 9), using a solution of 10 mMFe(CN)₆ ⁴⁻/0.1 M KCl and a scan rate of 0.01 V/s.

FIGS. 10-11 are comparisons of the chronoamperometric current (dottedline) of a single ring/fiber electrode (FIG. 10) and a microelectrodearray with the limiting current predicted by Szabo (FIG. 11) using asolution of 10 mM Fe(CN)₆ ⁴⁻/0.1 M KCl.

FIG. 12 is a diagram of development of electrochemiluminescence (ECL)intensity on an optoelectrochemical microarray, showing a voltammogram(a) and a corresponding ECL curve (b), with a scan rate of 2 mV/s and asolution of 1 mM Ru(bpy)₃ ²⁺/0.1 M TPrA/0.15 M phosphate buffer (pH 7).

FIG. 13 is a diagram of a calibration curve for ECL using the microarrayshown in FIG. 2, with E_(app)=1.2 V/Ag/AgCl using a solution of x mMRu(bpy)₃ ²⁺/0.1 M TPrA/0.15 M phosphate buffer (pH 7), where each pointshown is an average of 5 trials.

FIG. 14 is a schematic diagram of alternative electro-optical array tothat shown in FIG. 2.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

The invention provides novel optoelectric and optoelectrochemicalmicro-ring arrays and techniques for fabricating such arrays. The arraysinclude multiple optical fibers coated with electrically conductingmaterial, to serve as microelectrodes disposed about the optical fibers.An exemplary array was fabricated and tested. The array was fabricatedby coating individual optical fibers of 25 μm diameter with a 1 μm layerof gold nanoparticles via electroless gold deposition. A self-assembledthiol monolayer (SAM layer) around the individual gold-coated imagingfibers helped prevent electrical contact with neighboringring-electrodes. To achieve better mechanical stability and to make thedevice more practical, the electrode/fiber bundle comprisingapproximately 600 individual gold-coated optical fibers was dipped intoepoxy. By polishing the ends of such a device, a ring microelectrodearray comprising 600 individual and insulated ring electrodes wasformed. To limit diffusional overlap of current, only 20-30% of themicro-ring fiber/electrodes were wired. The inner diameter of the ringelectrode is fixed by the diameter of the individual optical fibers (25μm), while the outer radius is determined by the thickness of thedeposited gold. The array was characterized using ferrocyanide inaqueous solution as a model electroactive species to demonstrate thatthis microelectrode array format exhibits steady state currents at shortresponse times. In addition, cyclic voltammetry experiments wereperformed using conventional potentiostats due to the amplification ofcurrent inherent in the array format. Electrochemiluminescence (ECL) atthe ring electrode array was demonstrated through the oxidation ofRu(bpy)₃ ²⁺ in tri-n-propylamide in a pH 7 phosphate buffer solution,where the light generated was collected and detected via the fiberbundle.

Referring to FIG. 1, a system 10 includes a controller 12, an opticalactuator/sensor (A/S) 14, an electrical actuator/sensor (A/S) 16, aprocessor 18, an electro-optical array 20, and a subject 22. Thecontroller 12 is, e.g., a computer, and is configured to provide controlsignals to the optical A/S 14 and the electrical A/S 16. These controlsignals may be in response to information provided to the controller 12from the A/Ss 14, 16. The processor 18 is configured to obtaininformation from the A/Ss 14, 16 and process this information intomeaningful results for a user of the system 10. The optical A/S 14includes a charge-coupled device (CCD) camera 15 (see FIG. 2) as thesensor and a light source as the actuator. The actuator portion of theelectrical A/S 16 is a potentiostat.

The potentiostat is a PGSTAT 30 Autolab (made by Eco Chemie of Utrecht,Netherlands). The potentiostat is configured to apply DC voltages to thearray 20, e.g., ramping from a lower voltage to a higher voltage andreturning to the lower voltage. For example, the potentiostat can applyelectricity of voltages starting at 0 V, increasing to 0.6 V, andreturning to 0 V, at a rate of 0.02 V/s.

Referring also to FIG. 2, the array 20 is a bundle of fiber/electrodepairs 27 of optical fibers 24 with conductive coatings formingelectrodes 26 around the fibers 24. The fibers 24 are raw glass made offused silica glass from Edmund Industrial Optics of Barrington, N.J.Each fiber 24 has a 25 μm diameter and a length of about 10 cm.Approximately 600 fibers 24 are disposed in the array 20. The fibers 24can transfer light from a distal end 32 to a proximal end 34, and viceversa. The distal end 32 and the proximal end 34 are both preferablyrelatively flat in order to properly focus light/electricity to/from thesubject 22 at the distal end 32 and to/from the optical A/S 14 and/orthe electrical A/S 16 at the proximal end 34. The fiber pairs 27 are notcoherently related at the distal and proximal ends 32, 34. That is, itis unknown which distal end corresponds to which proximal end of asingle fiber pair 27 (the distal and proximal ends of each fiber pair 27do not appear in the same location of the distal and proximal ends 32,34 of the array 20). The fiber pairs 27 are embedded in epoxy 40 thatholds the pairs 27 together.

The electrodes 26 are gold and are coaxial with the fibers 24, extendingalong the cylindrical lengths of the fibers 24. Although gold has someadvantages, e.g., good deposition properties, numerous otherelectrically-conductive material is acceptable including, but notlimited to, silver, platinum, and electrically-conductive polymers(e.g., polythiophenes, polyanilines, and polypyrroles). Typicalthickness of the gold plating is about 0.3 m; thus, the electrodes 24have a typical outer radius of 12.8 μm (with an inner radius beingapproximately 12.5 μm, the diameter of the fibers 24). As shown in FIG.2, the electrodes 26 extend partially along the lengths of the fibers 24(with six of the electrode/fiber pairs indicated, for clarity). Acontact layer is connected to the set of electrodes 26 where thedeposited gold layer extends further than the other electrodes 26 (toallow only about 33% of the electrodes to be connected). Alternatively,only about 33% of the total fiber bundle can be coated with gold, thecoated fibers mixed with the non-coated fibers, and the contact layer 28connected to the coated fibers. A wire 30 couples the contact layer 28to the electrical A/S 16.

The subject 22 can be a substance and/or an object such as a person.Preferably, the subject 22 is or contains a substance that reacts toeither light or electricity and responds to this stimulus by emittingenergy in the other form, i.e., responding to light be emittingelectricity or responding to electricity by emitting light(electrochemiluminescence (ECL)). For example, the subject 22 can be aperson with an injected antibody that reacts to electrical stimulationby luminescing. Additionally, the subject 22 can be a sample solution tobe analyzed.

Assembly

Referring to FIG. 3, with further reference to FIG. 2, a process 50 ofmaking the array 20 includes the stages shown. The process 50, however,is exemplary only and not limiting. The process 50 can be altered, e.g.,by having stages added, removed, or rearranged. For the process 50,SnCl₂, tris(2,2′-bypyridyl)ruthenium (II) chloride hexahydrate,tri-n-propylamine, 11-mercapto-1-undecanol, trifluoroacetic acid,formaldehyde, H₂SO₄, AgNO₃, Na₂SO₃, H₂O₂, NH₄OH, methanol, ethanol,nitric acid from Sigma-Aldrich of Highland, Ill., and a commercialgold-plating solution (Na₃Au(SO₃)₂ Oromerse SO Part B, (5.67 g/100 ml)from Technic Inc. of Cranston, R.I., may be used.

At stage 52, approximately 600 of the fibers 24 are cut to lengths ofabout 10 cm and bundled at the proximal end 34. Bundling is accomplishedusing a 1 cm rubber tube acting as an O-ring.

At stage 54, the fibers 24 are plated with gold by having goldnanoparticles deposited around the surface of the individual opticalglass fibers 24. The particles are deposited using an electrolessdeposition method similar to that described in Kobayashi et al.,Analytical Chemistry, 1999, vol. 71, page 3665. The fibers 24 areimmersed into ‘piranha solution’ (70% H₂SO₄, 30% H₂O₂), rinsed withwater and methanol, and dried (Caution: ‘piranha solution’ reactsviolently with organic materials). These cleaned fibers 24 are immersedfor approximately 20 minutes into a solution of 0.026 M SnCl₂ and 0.07 Mtrifluoroacetic acid in 50% v/v methanol/water. This procedure depositsa Sn²⁺ “sensitizer” onto the glass surface of the fibers 24. The fibers24 are thoroughly rinsed with methanol and immersed into an aqueoussolution of ammonical AgNO₃ (0.035 M) for 15 minutes. This leads to thedeposition of silver nanoparticles on the fibers 24 while oxidizing thesurface-bound Sn²⁺ to Sn⁴⁺. The silver-deposited fibers 24 were rinsedwith methanol and water. These silver-coated fibers 24 are immersed,while stirring, in an aqueous solution of 0.079 M Na₃Au(SO₃)₂, 0.127 MNa₂SO₃ and 0.625 M formaldehyde for about 60 minutes in a water bath of4° C. Formaldehyde is oxidized catalytically by the silver particles andgold is reduced concurrently to elemental gold and deposited on thefiber surface. The gold-coated fibers 24 are rinsed thoroughly withwater and immersed, e.g., overnight, into 25% nitric acid solution todissolve residual Ag and Sn particles exposed on the surface of thefiber 24. The gold-covered fiber is rinsed with methanol and water, anddried. The final products, the electrodes 26, are dark red to goldenyellow, depending on the thickness of the gold coatings.

At stage 56, a self-assembled monolayer (SAM) is deposited on thesurface of the gold-coated fibers 27 to insulate the pairs 27. The SAMis deposited by immersing the pairs 27 into ethanolic solutionscontaining 10 mM 11-mercapto-1-undecanol. This helps to prevent eachfiber pair 27 from electrically contacting other fiber pairs 27.

At stage 58, the insulated fiber pairs 27 are bound to help furtherprocess and use the bundled fiber pairs 27. These insulated fiber pairs27 are dipped into an epoxy polymer that is cured at 100° C. in an ovenfor several hours. For example, Araldite AM 136/Hy 994 insulating epoxyfrom Ciba Geigy of East Lansing, Mich. may be used. The coating helpsenable polishing of the distal ends 32 of the fiber pairs 27. Thecoating also helps ensure total light reflection in the fibers 24. Thefiber pairs 27 are bound such that their center-to-center spacing isabout 30-100 μm to help ensure that diffusional overlap at longerelectrode-stimulation times is reduced such that it can be considered tobe negligible, and therefore not accounted for. For example, it has beensuggested that for diffusion to be neglected, the ratio of theedge-to-edge interelectrode distance d to the radius r of the electrodehas to be d/r≧20. To meet this criteria in this case, an average spacinggreater than or equal to r*20=(12/5 μm)*20=250 μm is needed.

At stage 60, approximately 20-30% of the electrodes 26 are electricallywired to the copper wire 30 through the contact layer 28, here a silverpaste. For example, epo-tek H20E from Epoxy Technology of Billerica,Mass. may be used. The silver paste is applied only to the longerelectrodes, and the wire 30 is electrically connected to the layer 28,e.g., by inserting the wire 30 into the paste 28 before curing of thepaste 28. Connecting less than all of the electrodes 26 for coupling tothe electrical A/S 16 helped to minimize diffusional overlap at longerstimulation times of the electrodes 26.

At stage 62, the ends 32, 34 of the array 20 are polished. The array 20is polished with 30-15-3-0.3 μm lapping films made by General FiberOptics of Fairfield, N.J. to expose the ring electrodes 26 around theoptical fibers. The polishing also helps ensure a planar surface at theends 32, 34 for proper focusing of light.

Operation

In operation, referring to FIG. 4, with further reference to FIGS. 1-2,a process 70 for stimulating the subject 22 and measuring and processingthe response using the system 10 includes the stages shown. The process70, however, is exemplary only and not limiting. The process 70 can bealtered, e.g., by having stages added, removed, or rearranged.

At stage 72, the array 20 is positioned for stimulating and measuringthe subject 22. The distal end 32 of the array is inserted into thesubject 22, e.g., a person. If desired, a chemical, such as an antibody,is injected into the subject 22 in the vicinity of the distal end 32 ina region to which the array 20 can apply electrical and/or opticalstimuli to the chemical and from which the array can receive electricaland/or optical responses.

At stage 74, a stimulus is provided to the subject in the vicinity ofthe distal end 32 of the array 20. The controller 12 sends signals tocause the optical A/S 14 to provide light to the proximal end 34 of thearray 20 and/or to cause the electrical A/S 16 to provide electricity tothe electrodes 26. Both light and electricity can be applied to thesubject 22 concurrently via the array 20. The stimuli are carried by thefibers 24 and/or the electrodes 26 and are radiated by the distal end 32of the array 20 into the subject 22.

At stage 76, the array 20 measures the reaction by the subject 22. Thesubject 22 responds to the stimuli provided by the array 20 by emittingelectricity and/or light. The emitted energy is received by the distalend 32 of the array 20 and transferred along the fiber pair 27 towardthe proximal end 34 of the array 20. Optical and electrical energy canbe sensed concurrently or one at a time. Optical and electrical energysensed concurrently can be sensed independently such that the sensedenergies can be distinguished. If the energy transferred along the fiberpair 27 includes electrical, then the contact layer 28 conveys theenergy to the wire 30 to the electrical A/S 16. If the transferredenergy includes light, then the light is conveyed from the proximal end34 to the optical A/S 14, and in particular an optical sensor such as aCCD camera.

At stage 78, the measured energy from the subject 22 is processed. Theoptical A/S 14 and/or the electrical A/S 16 output indicia of themeasured response to the processor 18. The processor 18 receives theseindicia, processes the indicia in accordance with stored software, andoutputs information, indicative of the subject's response, for a user.

Use

Arrays of sensors/actuators are used for various applications. Usingmultiple sensors/actuators with an array, multiple portions of a system(e.g., cell, analyte, material, or person) may be stimulated or measuredsimultaneously and independently by using disparate portions of thearray.

An optoelectrochemical microarray is used for industrial detectionpurposes, as well as clinical diagnostic and therapeutic applications.For example, the array is useful to gather data fromelectrochemiluminescence-based assays in which chemical compounds emitlight when electrochemically stimulated.

Compositions are addressed electrochemically and measured optically.Alternatively, compositions are addressed optically (or photochemically)and measured electrically. Fluorescent or light-emitting compounds suchas ruthenium metal-based compounds, ruthenium tris-bipyridyl compound(Ru(bpy)³²⁺), are used as labels for sensing biological compounds insensitive and precise assays. Other fluorescent or light-emittingcompounds include oxo-Mo(IV) complexes [Mo(Tp(Me,Me))(O)Cl(L)] (L=py,phpy or monodentate bpy; abbreviated as Mo(py), Mo(phpy), and Mo(bpe),respectively), Nile Blue, daunomycin,1,1′-bis(diorganophosphino)ferrocene-osmium(II) complexes, Rhenium(I)coordinated lumazine and pterin derivatives, porous silicon, conductingpolymers (e.g polythiophenes, polyanilines, polypyrroles,poly(2,5-dioctyloxy-p-phenylene vinylene)). Numerous other labels areknown in the art and are commercially available, e.g., from MolecularProbes, Inc. of Eugene, Oreg. Typically, the labels are excited whenexposed to an electrical current, e.g., at the surface of an electrodein an array; upon excitation, the compound emits light and isregenerated. Labels may undergo several excitation/emission cycles,thereby amplifying the light signal and increasing sensitivity. Anamount of analyte in a sample is determined by measuring the emittedlight and correlating the intensity of emitted light with theconcentration of analyte. Examples of tags that are addressedphotochemically and measured electrically include methylviologen andother viologens, porous silicon, and conducting polymers (e.g.,polythiophenes, polyanilines, polypyrroles,poly(2,5-dioctyloxy-p-phenylene vinylene)).

The array is used to gather data from in vivo or in vitro immunoassays.A photon-emitting tag such as a fluorescent compound conjugated to anantibody or other specific ligand is used to detect a particular celltype or release of a particular compound, e.g., a cytokine orneurotransmitter, by a cell. For example, a fluorescent tracer isinfused into brain tissue, and the microarray assembly is used tolocally measure release of neurotransmitters by measuring light emissionfrom the fluorescent tracer. The device yields qualitative as well asquantitative data regarding the analyte. For diagnostic purposes, atumor-specific antibody tagged with a light-emitting compound such asruthenium tris-bipyridyl compound (Ru(bpy)³²⁺) is injected or infusedinto a bodily tissue, and the antibody allowed to bind to its cognateligand. After washing or clearing of unbound antibody, the microarrayassembly is used to electrically stimulate the area to be diagnosed.Cells to which antibody is bound (i.e., tumor cells) emit light, whichis detected by the array. Thus, diagnosis/detection of cells expressinga tumor antigen is accomplished on a cell-by-cell basis.

The array is also used to electrically excite a specific cell (e.g.,identified optically using a cell-specific tag as described above)without exciting neighboring or adjacent cells, which have not beentargeted for pulsing. Similarly, the array is used to preferentiallydestroy or inhibit the growth of specific cells (e.g., which have beenidentified optically) without affecting neighboring or adjacent cellswhich were not targetted for growth inhibition or destruction. Followingdetection of individual cancer cells, a pulse of electricity isspecifically administered to the tumor cells, while sparing non-tumorcells in the tissue. The specificity of the therapeutic methods exceedsmost traditional therapies. Prior or simultaneous identification oftarget cells and destruction/excitation of specific target cells(without affecting “non-target” cells) reduces unwanted side effects(e.g., destruction of healthy “non-target” cells) often associated withtraditional cancer therapies.

Experiments

Experiments were performed using the system 10, with array 20 being asdescribed above. The array 20 included approximately 600 fibers of 10 cmlength and 25 m diameter. The fibers 24 were gold-plated to form theelectrodes 26. Approximately 20-30% of the electrodes 26 were connectedthrough the contact layer 28 to the wire 30. The fibers 24 were embeddedin an insulating polymer and the distal end 32 of the array 20 waspolished to expose gold-ring microelectrodes. The array 20 of micro-ringelectrodes was characterized using FE-SEM. Cyclic voltammetry andchronoamperometry were performed to characterize the electrochemicalbehavior of the micro-ring array. The array 20 was examined for itsapplicability for spectro-electrochemical problems. Subjects 22 of anaqueous Fe(CN)₆ ⁴⁺ solution and electrogenerated chemiluminescence withtris(2,2′-bypyridine)ruthenium (II) (Ru(bpy)₃ ²⁺) in the presence oftri-n-propylamine (TPrA) were used.

The instrumental set up for imaging and fluorescence measurements isdescribed in detail in Bronk et al., Analytical Chemistry, 1995, vol.67, p. 2750. The array 20 was fixed in a cell (V=1 ml) containing thecounter electrode of the potentiostat (e.g., a platinum wire) and thereference electrode of the potentiostat (e.g., a silver wire) andmounted on the stage that supports the imaging system 10 and the subject22. No excitation wavelength was used as Ru(bpy)₃ ²⁺ was excitedelectrochemically. The ECL returning through the optoelectrochemicalarray 20 was transmitted through a dichroic mirror and detected by a CCDcamera (model PXL-37 made by Photometric of Tucson, Ariz.). The emissionwavelength for Ru(bpy)₃ ²⁺ is 670 nm. Images were collected every 500 msfor 400 ms either by scanning the potential from 0.8 to 1.3 V/Ag/AgCl(scan rate=0.02 V s⁻¹) or by applying a potential of 1.2 V/Ag/AgCl tothe array 20. SEM images were obtained with a field emission scanningelectron microscope (FE-SEM; model 982 made by LEO Electron Microscopy,Inc. of Thomwood, N.Y.) located at Harvard University.

The potentiostat used was a PGSTAT 30 Autolab (made by Eco Chemie ofUtrecht, Netherlands). Experiments were performed using either a SCE orAg/AgCl reference electrode. The counter electrode was a platinum wire.Solutions were purged with nitrogen. In all experiments, a low-currentamplifier and a Faraday cage were used (model C2 made by BioanalyticalSystems, of West Lafayette, Ind.).

SEM

FIG. 5 shows an FE-SEM of some fiber electrodes 26 of the randomassembly embedded in the epoxy structure 40. The fibers 24 are insulatedfrom their neighbors by the epoxy 40. The center-to-center distance ofthe fibers 24 is between about 30 and 100 m. This distance would be tooclose to avoid diffusional overlap at longer electrode-stimulationtimes. This overlap was overcome by connecting only about 20-30% of thefiber/electrodes 27. FE-SEM was further used to visualize the gold layeraround the ring. As the optical fibers 24 are not conducting, chargingeffects are seen in FIG. 6. The gold ring is seen as the bright regionaround the optical fiber 24 and its thickness is estimated as beingroughly 300 nm.

Cyclic Voltammogram

When designing random assemblies of electrodes, care should be taken toavoid diffusional interference between adjacent electroactive areas. Acareful design is preferred if an assembly of micro-ring electrodes isto show steady state currents that are several times larger than asingle microelectrode. Such a device, based on the electrolessdeposition of gold around optical fibers, was formed by connecting only20-30% of the 600 gold-covered fibers in the bundle. This procedurehelped to maximize the preference for the individual rings to be spacedby ca 250 m, so that interferences due to diffusional overlap would bereduced, and possibly minimized.

Steady-state current-potential curves were recorded, enablingdetermining the number of active electrodes in the array and obtainingsome indication about the spacing between electrodes. FIG. 7 showscyclic voltammograms of a disk electrode (r=12.5 m) and a gold-particlecoated single fiber (r=12.5 m+0.3 m gold) polished on its end to exposea micro-ring electrode. The micro-ring fiber/electrode shows a sigmoidalwaveform at slow scan rates. An initial estimate of the size of theelectrode ring can be made by measuring the steady state currenti_(disk) recorded with a disk microelectrode of the same outer radius bthrough its steady state current and applyingi _(disk)=4nFD _(Fe(II)) c _(Fe(II)) b.  (1)In equation (1), n is the number of electrons, F is the Faradayconstant, D is the diffusion coefficient (D_(Fe(II))=6.0×10⁻⁶ cm s⁻¹), cthe concentration of the electroactive species (c=10 mM), and b theouter ring radius (b=12.8 m) respectively.

According to Wallingford et al., Analytical Chemistry, 1988, vol. 60, p.1972, the limiting steady-state current of a ring can be predicted fromthe current of a disk electrode of equal radius. Taking account of the300 nm gold layer around the fiber (b=r_(fiber)+300 nm gold), the outerradius of the ring/fiber is b=12.8 m and the current should reach aplateau at 2.96×10⁻⁸ A for a disk electrode. As seen in FIG. 7, however,the current recorded on the micro-ring is slightly lower compared to adisk electrode with the same outer radius. The numerical difference insteady state current for the ring compared to the disk electrode isabout 67%. It has been shown that for a ratio of inner radius/outerradius a/b=0.97, the ring current is only 68% of the disk, a value thatcompares nicely with ring electrode implemented here, with a=12.5 m andb=12.8 m. Therefore a ring-disk-shaped electrode with inner radius a andouter radius b should result in 33% smaller currents than a comparabledisk electrode with the same radius b.

The current of a single gold-coated fiber ring was used as a referencefor estimating the number of active rings in the high-density array.Ideally, an array with N active microelectrodes should yield a currentamplification relative to a single electrode by a factor of N.i _(array) =N*i _(micro)  (2)

In practice, these expectations are fulfilled only if certain verystrict requirements concerning the array design are met. If theelectrodes 26 are too closely packed, their diffusion layers willoverlap and the current response approaches that of a macroelectrode.

FIG. 8 shows the voltammogram of the microelectrode array 20 in a 10 mMaqueous solution of ferrocyanide. The steady state current responseswere preserved in this array format and give a useful qualitativeindication that the spacing between the active ring sites is sufficientsuch that the diffusion fields do not overlap, at least substantiallyso. Some overlap of diffusion layers may still take place as thearrangement of the electrodes and its connection was random and provedto be difficult to control. Depending on the particular array 20, someareas of the device have electrodes 26 that are clustered, while inother parts the distance for non-diffusional overlap is observedentirely. Furthermore, if two electrodes 26 touch each othermicroelectrode behavior would be observed with steady state currents, asthe final diameter of these ring fiber electrodes would be 50 m. Asthere are approximately 200 ring electrodes 26 in the array 20, theerror in the steady state current should be minimal. The limitingcurrent was used as an indication and a first approximation of thenumber of active sites on the array 20. The number of active sites N isestimated by dividing the limiting current of the array 20 by thelimiting current for a single fiber electrode 26 (FIG. 7) performedunder the same conditions. Using this assumption, it was estimated thatabout 200 micro-ring electrodes 26 were active.

As discussed above, the cyclic voltammogram (CV) shows thecharacteristic shape for spherical and nonplanar diffusion atmicroelectrodes and suggests that the majority of the electrodes 24 areseparated and that the diffusion layers do not overlap significantly. Ifinterelectrode spacing was not large enough, a characteristicmacroelectode shaped CV peak would have been observed. The incompletereversibility of the steady state current might be an indication thatsome electrode profiles may overlap. The SAM layer was important inobtaining these steady state results. FIG. 9 shows the CV of an assemblywhere the gold-deposited array was only sealed into epoxy. As seen inthe figure, the current height of the device is the same, but instead ofan expected steady state current, a peak shaped CV was observed. Thisresult can be explained by the fact that some of the electrodes 26 werein close contact leading to a characteristic macroelectrode response.

Chronoamperometry

To verify the assumption that large spacing between the individual ringsexists, chronomamperometric measurements were undertaken. The currentvs. time dependency of a micro-ring electrode can be considered as alimiting case of a band at short times and a disk microelectrode atlonger electrode-stimulation times. The current on a micro-disk and amicro-ring electrode can approach a steady state value while the currenton a band microelectrode decays with the reciprocal logarithm of time.Similar to a band electrode, the ring microelectrode has a higherperimeter-to-area ratio than the disk microelectrode. Many contributionshave been devoted to developing a theory of the diffusion controlledsteady-state current lim i(t) of bands and disks. The steady statebehavior for a ring electrode has been described in Szabo, J. Phys.Chem., 1987, vol. 91, p. 3108 and Fleischmann et al., J. Electroanal.Chem., 1987, vol. 222, p. 107, where lim i(t) was calculated assuminguniform accessibility to the surface of the ring electrode of arbitrarythickness. According to Szabo, the limiting current at time t at amicro-ring is given bylimi(t)=nFDcl ₀[1+l ₀/(4² Dt)^(1/2) ]l₀=[²(a+b)/ln[32a/(b−a)+exp(²/4)]  (3)

-   -   where a is the inner ring radius, and b is the outer ring        radius, respectively. This treatment assumes that the insulating        sheet is infinitely thick and a uniform flux to the surface of        the electrode 26 is maintained.

Chronoamperometric curves of one of the optical fibers coated with goldnanoparticles was recorded in 10 mM aqueous ferrocyanide solutions fortimes up to 5 s (FIG. 10). The experimental data shown in FIG. 10(points) are in good agreement with the theoretically calculated ones(line) using equation (3) with the respective variables being:D_(Fe(II))=6.0×10⁻⁶ cm s⁻¹, c=10 mM, a=12.5 m and b=12.8 m. In the caseof a micro-ring array, the chronomamperometric response depends on thetime frame of the experiment. At short times, where each individual ringis separated and no interference from overlapping diffusion is expectedif the interelectrode distance is sufficiently large, the current decayshould be 1/sqr(t), as described by Szabo and show Cotrellian behavior.From the chronoamperometric signal of the array in FIG. 11, this valueseems to be indeed the case if it is assumed that there are 200individual active electrodes and the limiting current is multiplied bythis factor. At longer times a more complex behavior is expected,changing from Cotrellian to cylindrical diffusion behavior (1/lnt) andfinally to planar diffusion of the whole array (1/sqr(t),), resembling amacroelectrode.

If the thickness of the micro-ring is assumed to be 300 nm, the typicaltime expected to reach steady state current is in the order of l²/D²⁶,where l is the characteristic dimension of the electrode 26. In the caseof a ring, l is taken as the inner radius a of the ring and the timecalculated to reach steady state behavior is 0.26 s, which is feasibletaking into account that steady state currents develop rapidly atmicroelectrodes. Taking equation (4) as an approximation for thedimension of the diffusion layer developed on the ring, the thickness ofwill be 12 m. This value corresponds to the inner radius a of thering/fiber electrode.=sqr(Dt)  (4)

At 5 s, would have grown to around 60 m so that if the spacing betweenthe electrodes is larger than 60 m, no diffusional interferences andtherefore no macroelectrode behavior will be observed, as shown in FIG.12.

Electrogenerated Chemiluminescence

Electrochemical oxidation of Ru(bpy)₃ ³⁺ results in chemiluminescence inthe presence of TPrA. Novel spectroelectrochemical sensors embodying twomodes of instrumental selectivity, electrochemical and spectroscopichave been described by Gao et al., Electroanalysis, 2001, vol. 13, p.613. A critical review of the analytical applications of Ru(bpy)₃ ³⁺ asa chemiluminescent reagent has recently been published by Gerardi etal., Anaytical Chim. Acta, 1999, vol. 378, p. 1. Theelectrochemiluminescence (ECL) of an electrolyte solution results fromthe electron transfer reaction of ion radicals produced from an organicreactant that generates an excited state product and luminescence whenit relaxes to its ground state. The ECL intensity is a quantitativecharacteristic of the rate of such an electron transfer reaction.

The aqueous system of Ru(bpy)₃ ²⁺/TPrA was used to demonstrate that themicro-ring optical fiber array 20 can be used for the detection oflight. The ECL mechanism of this system has been intensivelyinvestigated. At high concentrations of Ru(bpy)₃ ²⁺ (>0.1 mM) thecatalytic oxidation of TPrA by electrogenerated Ru(bpy)₃ ³⁺ is thedominant process of ECL as described by the following equations:Ru(bpy)₃ ^(2+→)Ru(bpy)₃ ³⁺ +eE ⁰=1.26 V/SCE  (5)Ru(bpy)₃ ³⁺ +TPrA ^(→)Ru(bpy)₃ ²⁺ +TPrA ⁺  (6)TPrA ⁺ →TPrA ^(•) +H ⁺  (7)Ru(bpy)₃ ³⁺ +TPrA ^(•)→Ru(bpy)₃ ²⁺*+products  (8)Ru(bpy)₃ ²⁺*→Ru(bpy)₃ ²⁺ +hν  (9)

To perform ECL, the assembly 20 was placed into a voltammetric cell,comprising a 1 ml volume. A platinum plate counter electrode was placedparallel to the device. This positioning ensured that no reflected lightfrom the platinum surface would be collected by the optical fibers. ECLwas performed by stepping the potential from 0.0 V/Ag/AgCl, where noelectrochemical reaction takes place, to 1.20 V/Ag/AgCl where oxidationof Ru(bpy)₃ ²⁺ and the catalytic oxidation of TPrA occurs (FIG. 12). TheECL intensity increased rapidly at a potential more positive than 1.0 Vreaching a constant level from 1.10-1.30 V/Ag/AgCl. Light was collectedat 550-650 nm, the emission region of the Ru(bpy)₃ ³⁺. When thepotential was held constant at 1.20 V/Ag/AgCl the signal was stable formore than a minute before the fluorescence signal decayed. The rise inECL emission reaches a steady state, but at times longer than the steadystate of the diffusion layer, which was estimated as being 0.23 s (seechronoamperometry). ECL emission increases via an initial fast riseoccurring at time constants on the order of 0.23, followed by acomparatively slow increase to the steady state limit. In this manner,the electrochemical properties of the ring and its ability to collectlight with the same device were demonstrated.

The analytical utility of the chemiluminescence of Ru(bpy)₃ ²⁺ dependson the emission of light, which is indicative of the concentration ofthe analyte in solution. The microarray was therefore exposed todifferent Ru(bpy)₃ ²+concentrations. FIG. 13 shows a calibration curvefor the ruthenium system using the microarray. To obtain reproduciblesignals, after each trial, the electrode was cleaned by pulsing itseveral times to remove any adsorbed or deposited materials.

CONCLUSION

The array tested demonstrated that electrochemically-generatedluminescent products can be detected with a fiber assembly. This devicecan be used as an optoelectronic sensor, especially for the electrolyticgeneration and transmission of ECL. While all the fibers 24 wereoptically addressable, not every fiber was electrochemicallyaddressable. The resolution of the device was in the tens of micrometersrange, determined by the diameter of the optical fibers 24 and by thespacing between each electrically-connected fiber. For the purpose ofhaving well-behaved microelectrode characteristics, this spacing wasdesigned to be larger than 60 m. An ordered optoelectrochemical devicemay overcome this limitation and should allow chemical andelectrochemical sensing as well as imaging of surfaces with good spatialresolution

Other embodiments are within the scope and spirit of the appendedclaims. For example, due to the nature of software, functions describedabove can be implemented using software, hardware, firmware, hardwiring,or combinations of any of these. Features implementing functions mayalso be physically located at various positions, including beingdistributed such that portions of functions are implemented at differentphysical locations.

Additionally, while the array 20 was described as being non-coherent andwith electrode rings 26 disposed about optical fibers 24, an array canbe coherent and/or have electrodes disposed within one or more opticalfibers. For example, referring to FIG. 14, an array 100 includeselectrodes 102, optical fiber rings 104, and epoxy 106 that holds theelectrodes 102 and rings 104 in place. The electrodes 102 arecapillaries filled with gold, or other suitable conductor. The rings 104comprise material that helps guide light between ends of the array 100.The electrodes 102 are connected by a contact layer 108, to a wire 110,for connection to an electrical A/S (see FIG. 1). A CCD camera 112 isdisposed near a proximal end of the array 100 for sensing lighttransferred through the array 100. The electrode/ring pairs 114 arecoherent in the array 100, with the spatial relationship of theapertures of the pairs 114 at the distal end 116 relative to theproximal end 118 being known. Preferably, the pairs 114 are arranged thesame at each end 116, 118 to help reduce processing of sensed energy atthe proximal end 118. The coherency helps the array 100 be used forimaging, e.g., optical imaging of subjects disposed in the vicinity ofthe distal end 116. To help avoid diffusional overlap, thecenter-to-center spacing d of the electrodes 102 should obey the d/r≧20guideline (d being the center-to-center spacing for solid electrodes 102versus the edge-to-edge spacing for ring electrodes 26).

An array of electrodes can be used with a single optical transmissionmedium that also holds the electrodes in place. For example, the array100 can be made using an optically-conductive, low-index-of-reflection(e.g., 1.56) substrate, in place of the epoxy 106, through whichpassages are formed. The passages can be clad with ahigh-index-of-reflection (e.g., 1.66) material, in place of rings 104.The clad passages can be filled with electrically-conductive material,such as gold, to form electrodes. The electrodes conduct electricity asdesired, and the substrate acts essentially as a single optical fiber inwhich the electrodes disposed. The substrate can thus transfer light inthe vicinity of the distal end of the array to the proximal end, withlight being produced in different portions of the distal-end vicinitycombining in the substrate.

Also, different amounts of optical fibers and electrodes, and differentamounts of active electrodes than as discussed above are acceptable. Forexample, an array can have more or fewer, e.g., 100, optical fibers thanthe 600 fibers discussed above. Further, the amount of active electrodescan be different, e.g., approximately 50% of the total number ofelectrodes. Other percentages or relative amounts of active versus totalelectrodes are possible, with the desire being that the inter-electrodespacing be such that diffusional overlap is substantially negligible.

1. An electro-optical system comprising: an array comprising: aplurality of optical fibers configured to transmit light, the opticalfibers being mechanically coupled at distal ends in a distal arrangementand mechanically coupled at proximal ends in a proximal arrangement; anda plurality of electrodes substantially coaxially disposed with at leastportions of corresponding optical fibers, the electrodes beingelectrically conductive, with the electrodes and optical fibers beingdisposed in pairs, thereby being pair components, with one of the paircomponents of each pair being disposed about a radial periphery of theother pair component; and an insulator disposed between the plurality ofelectrodes and configured to inhibit transfer of electrical energybetween the plurality of electrodes.
 2. The system of claim 1 furthercomprising: an electrical apparatus coupled to at least some of theplurality of electrodes and configured to at least one of transmitelectrical energy to, and receive electrical energy from, the at leastsome of the plurality of electrodes; and an optical apparatus configuredand disposed to receive light from the proximal ends of the opticalfibers.
 3. The system of claim 2 wherein the electrical device iscoupled to less than all the plurality of electrodes.
 4. The system ofclaim 3 wherein the electrical device is coupled to a percentage of theelectrodes such that diffusional overlap at distal ends of theelectrodes will be substantially negligible.
 5. The system of claim 4wherein the electrical device is coupled to approximately 20-30% of theelectrodes.
 6. The system of claim 1 wherein the electrode of each pairis disposed about the radial periphery of the fiber of each pair.
 7. Thesystem of claim 6 wherein an edge-to-edge spacing between any twoelectrodes coupled to the electrical apparatus is greater than about 10times a typical diameter of one the plurality of electrodes.
 8. Thesystem of claim 1 wherein the optical fiber of each pair is disposedabout the radial periphery of the electrode of each pair.
 9. The systemof claim 8 wherein a center-to-center spacing between any two electrodesdisposed coaxially with the at least some of the plurality of opticalfibers is greater than about 10 times a typical diameter of one theplurality of electrodes.
 10. The system of claim 1 wherein the distalends of the optical fibers correlate to the proximal ends of the opticalfibers in a known manner.
 11. The system of claim 1 wherein the distalarrangement and the proximal arrangement are substantially similar. 12.The system of claim 1 wherein the electrical apparatus is configured toat least one of transfer electrical energy to, and receive electricalenergy from, the at least some of the plurality of electrodes as agroup.
 13. The system of claim 1 wherein the electrical apparatus isconfigured to at least one of transfer electrical energy to, and receiveelectrical energy from, the at least some of the plurality of electrodesindividually.
 14. The system of claim 1 wherein the electrodes compriseelectrically-conductive material coating an outer surface of the opticalfibers.
 15. A method of stimulating and sensing an object, the methodcomprising: providing energy in a first form to the object through atleast one of a plurality of first energy transmitters disposed in afirst array at least at distal ends of the first energy transmitters,the first form of energy being one of electrical and optical; andsensing energy in a second form, produced by the object, through atleast one of a plurality of second energy transmitters disposed in asecond array at least at distal ends of the second energy transmitters,the first and second energy transmitters being mechanically coupledtogether and coaxially disposed at least at their distal ends, thesecond form of energy being one of electrical and optical, the secondform of energy being different than the first form of energy.
 16. Themethod of claim 15 wherein the first form of energy is electrical andthe first energy transmitters are microelectrodes, and wherein theproviding energy includes providing energy to all of the plurality offirst energy transmitters.
 17. The method of claim 15 wherein the firstform of energy is electrical and the first energy transmitters aremicroelectrodes, and wherein the providing energy includes selectivelyproviding energy to a portion of the plurality of first energytransmitters.
 18. The method of claim 17 wherein the providing energyincludes providing energy to the portion of the plurality of firstenergy transmitters such that diffusional overlap of the energy atdistal ends of the portion of the plurality of first energy transmittersis substantially negligible.
 19. The method of claim 15 wherein thefirst form of energy is electrical and the first energy transmitters aremicroelectrodes, and wherein the providing energy includes providingdifferent amounts of energy to different ones of the plurality of firstenergy transmitters.
 20. The method of claim 15 wherein either the firstor the second energy transmitters are electrodes, the method furthercomprising providing electrical energy through the electrodes to killliving tissue in the object in a vicinity of distal ends of theelectrodes.
 21. The method of claim 15 further comprising processing thesecond energy to determine an image of at least a portion of the object.22. The method of claim 15 further comprising providing energy in thesecond form to the object through at least one of the second energytransmitters.
 23. The method of claim 22 wherein the providing energy inthe first form and the providing energy in the second form occursconcurrently.
 24. The method of claim 23 further comprising sensingenergy in the first form concurrently with the sensing energy in thesecond form.
 25. The method of claim 15 wherein the second energytransmitters are optical fibers, and the sensing includes sensingoptical energy transmitted by at least two of the optical fibers. 26.The method of claim 15 wherein the first energy transmitters are opticalfibers and the providing includes transmitting optical energy throughless than all of the optical fibers.
 27. An electro-opticalactuator/sensor system comprising: optical means for delivering light toan optical-fiber array; electrical means for delivering electricitythrough an electrical array of microelectrodes, the electrical meanscomprising electrically-conductive cladding of the optical fibers in theoptical-fiber array; an electrical apparatus coupled to the electricalmeans and configured to transfer electrical energy between theelectrical apparatus and selected ones of the microelectrodes; and anoptical apparatus configured and disposed to transfer light between theapparatus and the optical-fiber array.
 28. The system of claim 27wherein distal and proximal ends of the optical fibers and electrodesare coherently related.
 29. The system of claim 27 wherein theelectrical apparatus is coupled to transfer electrical energy to about20-30% of the electrodes.
 30. The system of claim 27 wherein distal endsof the electrodes are disposed proximate to distal ends of the opticalfibers and are separated from each other such that diffusional overlapassociated with the electrodes is substantially negligible.
 31. Anelecto-optical array comprising: an optical substrate configured totransmit light, the substrate defining a plurality of openings extendingthrough a thickness of the substrate; a plurality of electrodes disposedwithin the openings through the substrate; and at least one electricalconductor coupled to a portion of the plurality of electrodes, the atleast one electrical conductor being configured to couple to anapparatus for supplying current to, and receiving current from, the atleast one electrical conductor.
 32. The array of claim 31 furthercomprising a plurality of optical rings disposed within the plurality ofopenings between the substrate and the electrodes, the optical ringshaving a higher index of reflection than the substrate.
 33. The array ofclaim 31 wherein the openings defined by the substrate extendsubstantially straight through the substrate.
 34. The array of claim 31wherein distal ends of the electrodes are disposed relative to eachother in a distal arrangement, and proximal ends of the electrodes aredisposed relative to each other in a proximal arrangement, and thedistal and proximal arrangements are substantially similar.
 35. Thearray of claim 31 wherein the portion of the electrodes is such thatdiffusional overlap from distal ends of the electrodes is substantiallynegligible.
 36. The array of claim 35 wherein the portion of theelectrodes comprises approximately 50% of the electrodes.
 37. The arrayof claim 35 wherein the portion of the electrodes comprisesapproximately 20-30% of the electrodes
 38. A method of specificallystimulating a target cell in population of non-target cells, comprisingdetecting an optical signal to identify said target cell and deliveringan electrical current to said cell, wherein said electrical current issubstantially not delivered to a non-target cell and wherein said targetcell is stimulated to transduce an intracellular or extracellularsignal.
 39. A method of specifically destroying a target cell inpopulation of non-target cells, comprising detecting an optical signalto identify said target cell and delivering an electrical current tosaid cell, wherein said electrical current is substantially notdelivered to a non-target cell and wherein said target cell isdestroyed.